N -Acetylcysteine and 15 Deoxy-Δ12,14 -Prostaglandin J2 Exert a Protective Effect Against Autoimmune Thyroid Destruction in Vivo but Not Against Interleukin-1α/Interferon γ-Induced Inhibitory Effects in Thyrocytes in Vitro

Reactive oxygen species (ROS) are crucial for thyroid hormonogenesis, and their production is kept under tight control. Oxidative stress (OS) is toxic for thyrocytes in an inflammatory context. In vitro , Th1 pro-inflammatory cytokines have already been shown to decrease thyroid-specific protein expression. In the present study, OS level and its impact on thyroid function were analyzed in vitro in Th1 cytokine (interleukin [IL]-1α/interferon [IFN] γ)-incubated thyrocytes (rat and human), as well as in vivo in thyroids from nonobese diabetic mice, a model of spontaneous autoimmune thyroiditis. N -acetylcysteine (NAC) and prostaglandin, 15 deoxy-Δ12,14 -prostaglandinJ2 (15dPGJ2), were used for their antioxidant and anti-inflammatory properties, respectively. ROS production and OS were increased in IL-1α/IFNγ-incubated thyrocytes and in destructive thyroiditis. In vitro , NAC not only reduced ROS production below control levels, but further decreased the expression of thyroid-specific proteins in addition to IL-1α/IFNγ-inhibitory effects. Thus, besides ROS, other intracellular intermediaries likely mediate Th1 cytokine effects. In vivo , NAC and 15dPGJ2 reduced OS and the immune infiltration, thereby leading to a restoration of thyroid morphology. It is therefore likely that NAC and 15dPGJ2 mainly exert their protective effects by acting on infiltrating inflammatory cells rather than directly on thyrocytes.